There are fairly significant differences between the Standard/Mark I, Mark II, Mark III, and Mark IV pistols, beyond that of the take-down design. Much moreso than are being reflected by commenters in this post. But spelling these out is not the question at hand.
So how are the new Ruger Mk IV .22 pistols doing on the range?
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I do not know much about Ruger .22 pistols, but do know the new Mk IV is easier to take apart to clean over older models. I am looking for a reliable and accurate .22 pistol for plinking and target practice, for fun. Maybe some day even small game hunting.
Are the new Mk IVs good to go? Do they have problems, are they good guns and should I get one?
I have 2 of the stainless bull barrel Mark IV's for my training courses, just the same as what you have pictured, except in stainless. Plus, I have a Competition (slab side) for myself, and my wife has a Hunter. I've relied upon the Ruger Mark Series in my training classes for over 15yrs, and have used one Mark II in particular to start out literally hundreds of new shooters.
The Mark IV's seem to be as accurate as any of the predecessors, which means they're as accurate or slightly moreso on average than any of the other target-style 22LR pistols on the market in their price class. And more often than not, they are more reliable than the competition with as broad or broader tolerance for ammo.
So... How are the Mark IV's doing on the range? Fabulously. Are they good to go? Yup. Do they have problems? None have been revealed so far. Are they good guns? Yup! Should you get one? Eh, up to you - if you have a want or a need for a target-style, relatively budget friendly 22LR pistol, then yes, the Mark IV is as good or better option than most other models.